Going green: 10 years of E³

When mechanized tamping switched to the use of hydraulics 70 years ago, this ushered in a new era in track maintenance. By using the non-synchronous constant pressure tamping principle and hydrostatic drive, energy efficiency of approx. 70% could be achieved for the first time. Plasser & Theurer continued to develop this basic idea over the last few decades, enriching it with new solutions for customer requirements: multi-sleeper tamping technology, continuous working action, or frequency control for tamping units are examples of important technological advancements. The switch from hydraulic to electric power can be seen as the next groundbreaking step.

In 2014 the drive system was expanded: using overhead-contact-line components to connect it to the traction current paved the way for potentially carbon-neutral operation. During the first step, it was possible to retain the machines’ established basic architecture. In addition to the diesel engine which supplies the energy for the hydraulic drive system, traction current was fed to an additional electric motor via the pantograph, transformer, and power converter. This heralded the arrival of the first evolutionary stage of Plasser & Theurer's E³ technology: the electro-hydraulic drive concept. It was the first time traction current could be used to power a track maintenance machine.

The percentage of renewable energy used for traction current in Germany is going up significantly; in 2022, it was 65.2%. In Austria, traction current is completely sourced through hydropower, sun, and wind. The contact wire serves as the perfect source of energy for track maintenance. A company which took on a pioneering role by using E³ technology in 2016 is Krebs Gleisbau with its Unimat 09-32/4S Dynamic E³. This tamping machine for plain-line tracks and turnouts provided data which quickly proved how environmentally friendly action can also be cost-effective.

The next step saw E³ technology continue to systematically develop into an all-electric system, which increased overall energy efficiency to approx. 83%. A 750 V DC supply link forms the backbone of the system. All-electric energy is distributed directly to the relevant consumers on the track maintenance machine. Electricity powers the on-board system, heating, ventilation, and air conditioning as well as all rotational movements. This also includes the traction drive (electric powered bogies), the work unit actuators (vibration drive of the tamping units and Dynamic Track Stabilizer), and electric propulsion of the satellite of a continuous-action tamping machine. The electric actuators enable performance increases thanks to increased repeatability, greater efficiency, and reduced maintenance costs. The hydraulic system continues to demonstrate its advantages in linear movements: efficient, robust, and with high power density. This combines the best of both worlds.

Due to the increasing demand for alternative drive systems in track maintenance, environmentally friendly CO₂-reducing solutions are now available in numerous areas of work. In the meantime, vehicles and machines for overhead-contact-line construction and maintenance as well as permanent way and superstructure maintenance are also being equipped with new E³ drive systems. In the case of tamping machines for plain-line tracks and turnouts, machines for ballast management, and machines for dynamic track stabilization, the ten-year technological edge is having a significant scaling effect for the railway system, especially in Europe.